非饱和粉质黏土冻结温度和冻结变形特性试验研究

为掌握冻土冻结变形规律,揭示冻结变形机理,采用自行研制的温控体变仪精确测量不同饱和度、孔隙比土样的冻结变形,为计算冻土的体积含冰量,对非饱和粉质黏土冻结温度进行了测量。室内试验结果及其数据分析表明:(1)非饱和粉质黏土冻结温度(冰点)主要由土样初始基质吸力决定,基质吸力越大,冻结温度越低。(2)非饱和粉质黏土冻结变形随饱和度变化存在两种截然不同的机制,饱和度较低时,冰水相变影响较小,土体呈冻缩特征;饱和度较高时,冰水相变占主导作用,导致土体结构破坏,呈冻胀特征。(3)非饱和粉质黏土冻结体应变与土体体积含冰量和初始孔隙比具有良好的经验关系,可以基于体积含冰量和初始孔隙比预测土体冻结体应变,其中体积含冰量由土体冻结温度、温度、饱和度、干密度计算得到。

Experimental study on freezing point and deformation characteristics of unsaturated silty clay subjected to freeze-thaw cycles

To obtain a predictive model of freezing deformation, three-dimension deformational tests are carried out to study the deformation characteristics of samples with various degrees of saturation and void ratios. To obtain the ice content in frozen soils, the freezing points of soils are also measured. The test results demonstrate that: (1) The freezing point of soils is mainly dependent on the initial matric suction of soils. (2) There are two different deformation phenomena for soils after being frozen: one is the frozen shrinkage if the degree of saturation of soils is low, the other is the frozen expansion if the degree of saturation is high. (3) The volumetric strains of soils after being frozen have a linear empirical relation with the ratio of volumetric ice content to initial void ratio of soils, where the volumetric ice content of soils can be calculated by the degree of saturation, freezing point, temperature and dry density of soils.